Small-crater counts on Mars light-toned sedimentary rock are often inconsistent with any isochron; these data are usually plotted then ignored. We show (using an 18-HiRISE-image, >10^4 crater dataset) that these non-isochron crater counts are often well-fit by a model where crater production is balanced by crater obliteration via steady exhumation. For these regions, we fit erosion rates. We infer that Mars light-toned sedimentary rocks typically erode at ~10^2 nm/yr, when averaged over 10 km^2 scales and 10^7-10^8 yr timescales. Crater-based erosion-rate determination is consistent with independent techniques, but can be applied to nearly all light-toned sedimentary rocks on Mars. Erosion is swift enough that radiolysis cannot destroy complex organic matter at some locations (e.g. paleolake deposits at SW Melas), but radiolysis is a severe problem at other locations (e.g. Oxia Planum). The data suggest that the relief of the Valles Marineris mounds is currently being reduced by wind erosion, and that dust production on Mars <3 Gya greatly exceeds the modern reservoir of mobile dust.

Mineral discovery explains Mars’ landscapeA Queen’s University researcher has discovered a mineral that could explain the mountainous landscape of Mars, and have implications for NASA’s next mission to the planet.

"Satellites orbiting Mars show us images of canyons and gullies that appear to have been created by a flood or rapid out-washing. Exploration rovers, currently moving about on the planet’s surface, also show us that there is no visible water on the surface of Mars, but that there was in the past" - Ron Peterson, Queen’s geologist.

Dr. Peterson suggests that Mars was likely wetter in the past. All of the images that are coming back from the rovers show layering in the rock which is indicative of sediment manipulated by water. This kind of out-wash would require a fair amount of water on the planet at some point.The study, published this week in GEOLOGY, a publication of the Geological Society of America, suggests that these findings may provide insight into how to retrieve a sample of Mars' surface and return it to earth.

The European Space Agency's Mars Express orbiter has mapped almost the entire planet for minerals that bear chemical fingerprints of past reactions with water.And it has found that less than 1 percent of the planet's surface shows signs of hydrated minerals.

"We initially thought hydrated minerals would be everywhere. That turned out to be not the case" - Jean-Pierre Bibring, the lead investigator for the Mars Express Omega instrument, which splits and analyses visible and near-infrared light radiating from the planet's surface.

For the past two years, Bibring and his team have been shifting through the Omega data for minerals that contain water in their crystalline structure. Two types of hydrated minerals have been found: phyllosilicates, which, like clay, develop from rocks that have prolonged contact with water; and sulphates, which form as deposits from saltwater.In general, the clays are more likely habitats for life than sulphates because they needed more time to interact with water to form.The search for life beyond Earth is shaped by the fact that life, at least forms of terrestrial life, needs water to develop. So on Mars, and elsewhere in the solar system, researchers have focused on finding suitable habitats for life to evolve, namely sites that have or had liquid water.On Earth, life has been found in a vast array of hostile environments, including around deep-sea vents.

"You don't need to be on the surface to have life appear" Jean-Pierre Bibring.

He suspects that a much richer supply of hydrated minerals exists just beneath the Martian crust.

"As soon as you have a way to drill, you might find the entire crust was exposed to water" - Jean-Pierre Bibring.

In a presentation to scientists at the Lunar and Planetary Sciences Conference in Houston, Bibring said he believes the phyllosilicates developed first on Mars. That layer was covered by red-hued soil due to a massive global disturbance. The sulphates formed later.

Scientists expect to get a much better understanding of the mineral makeup of Mars when NASA's Mars Reconnaissance Orbiter, which arrived at Mars last week, begins its mission later this year. The orbiter has a spectrometer that that has 10 times better resolution than Mars Express' Omega instrument.The Mars Reconnaissance Orbiter is scheduled to reach its operational orbit in November and then begin a detailed search for signs of water.

Basically, the lack of carbonates on the Martian surface, that should have formed in a once wet and carbon dioxide abundant mars, is due to the creation of sulphuric acid.The acid dissolved all the carbonates away leaving the sulphide salts on the surface as it dissolved away…

New data from the Mar orbiters cameras have picked up evidence of 21 more rivers with flows once comparable to similar-sized rivers on Earth today. That makes 28 rivers, total, that may have once flowed on Mars. Whether these long-dead rivers were carved by single deluges, a few pulsed floods or a relatively brief rainy climate some 3.7 billion years ago still remains a mystery.

"We were trying to determine how much water flowed through these valleys" - Rossman Irwin, Smithsonian Institution Mars researcher. A report on the newfound rivers appears in the June issue of the journal Geology. Even rough calculations of the water flow were almost meaningless in past years because the Mariner spacecraft imagery just wasn't good enough to peer into the bottoms of Mars' huge canyons and measure the actual channels in which water flowed. More recent data from the Mars Odyssey spacecraft has provided that channel view — along with clues about smaller tributaries.

By mapping out the tributaries and main channels of the dry rivers, Irwin and his colleagues were able to define the boundaries of ancient watersheds and calculate the amount of water — perhaps as rain — it would have taken to create the channels. "What you get is a centimetre of precipitation per day" -Rossman Irwin. That's a conservative number because there are a lot of unknowns — like how deep the rivers ran.

"We assumed they're fairly shallow" - Rossman Irwin. This is based on the shallow, meandering rivers found in desert areas on Earth. It's also clear that whatever created the wet conditions, it ended abruptly about 3.6 billion years ago. Evidence for that is the fact that the ancient tributary and river channels still exist.On a wet planet like Earth, such features would be quickly eroded away by rain and snow. "What we are looking at is the evidence of the last flows on Mars. The climate on Mars deteriorated very, very quickly." - Rossman Irwin.Previous studies of Martian water drainage features have come to similar conclusions, according to U.S. Geological Survey geologist Mike Carr, a prominent authority on Mars surface features.

"It looks like the Martian (drainage) systems are immature" - Mike Carr. In other words, they were either cut quickly with large floods or slowly with very infrequent flows. Either way, they didn't have the water power to develop into the large, finely branched drainage patterns found in the Mississippi or the Amazon basins on Earth. Nonetheless, "finding these (rivers) is comforting" - Mike Carr.

The new waterways confirm what many scientists had suspected would be found at the bottoms of those Martian canyons. It further supports the prevailing view that the Red Planet once had liquid water on its surface.

These rocks are so ancient that their sediments were deposited, cemented to form rock, and then eroded by the water (or other liquid) that carved Ladon Valles, so far back in Martian history that such liquids could still flow on the planet's surface.